The app does not require following some specific diet or eliminating some foods, but you can do that if you want to. This is up to your dietary preferences. Some people try to reduce carbs, some try to cut fats. Generally, you want to eat healthily and stay within your nutrition plan set up by you in the app to meet your weight goals. You can keep eating your favorite foods, but you may need to do this in moderation, to make sure your nutrition is balanced (see the USDA Food Pyramid guide for additional information about food groups.) The Food Grade helps quickly estimate healthfulness of each food. Premium Recipes allow to filter out the system recipes matched your diet.
To discover more about different diet types and how to set up the diet you decided to follow, see our article about Premium Diets.
To get diet advice, send a question in the "Ask RD" forum - the first row in Community.